1. Field of the Invention
This invention relates to a rotary pump adapted for pumping fluids, more particularly to a rotary pump which includes two meshing multi-lobe rotors disposed in a rotor chamber without contacting the latter.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a conventional rotary pump 20. The rotary pump 20 includes a housing 21 having an inner circular surface 212 that confines a rotor chamber 211. A vane-type rotor 22 is disposed eccentrically inside the rotor chamber 211. The rotor 22 is provided with a plurality of elongated grooves 221 which are arranged in a circumferential direction, and a plurality of vanes 222 inserted slidably in the grooves 221. The vanes 222 can be oil-lubricated steel blades or graphite blades. The rotor 22 is connected to an output shaft of a motor 10. A cooling device 11 is mounted on the output shaft of the motor 10. The vanes 222 are slid out of the grooves 221 by centrifugal force, and are pushed back into the grooves 221 by the inner surface 212 during the eccentric rotation of the rotor 22 in the rotor chamber 211.
The steel blades 222 used in the vane-type rotary pump described above, which require lubrication, may become fouled by the lubricant which degrades due to high temperature after being used for a period of time, and will be unable to operate smoothly. Under such circumstances, further operation of the pump 20 can cause severe damage to the blades 222 or even the pump 20 severely damaged.
In addition, when the pump 20 is applied in a printing press, if the lubricant starts to leak out from the pump 20 and splashes onto the paper sheets during printing, the pump 20 will have to be repaired or replaced with a new one.
If graphite blades 222 are used instead of steel blades 222, fine particles of carbon generated by attrition will occur, thereby causing pollution to the environment. Moreover, as the lubricant used in gearing and bearing systems and sealing rings will degrade due to high temperature caused by the friction during eccentric rotation of the rotor 22 in the rotor chamber 211, the degraded lubricant may permeate through the deteriorated sealing rings into the rotor chamber 211 and stick to the graphite blades 222. As such, the service life of the graphite blades 222 can generally be sustained for about one year, and frequent replacement is thus necessary.
Further, the pump 20 requires installation of a cooling device 11 to dissipate the heat generated by the friction described above, and special material for air inlet and outlet pipes. The pump 20 also has disadvantages in that it generates noise and consumes much energy.